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Objectives for NS 3:
You should be able to define, describe pathogenesis,
list lesions and know how to diagnose the following
conditions:
•Meningitis
•Rabies
•ITEME
•Distemper
•Listeriosis
•West Nile Viral encephalitis
•TSE
•Equine protozoal encephalomyelitis
Infectious diseases of CNS
Portal of entry
Blood
Nerves
Paracranial and paravertebral infections
(sinuses, ear, bones et cet)
Meningitis
• Et: E. coli, Streptococcus, Haemophilus
Cryptococcus, FIP virus etc.
• Most common in young animals (Bo, Po)
• Often as part of polyserositis
• Lesions: inflammatory exudate
• Diagnosis:
Gross (impression smear) and histology
Bacterial/fungal culture
Encephalomyelitis
There are many infectious agents
• Viral
• Bacterial
• Mycotic
• Protozoal
• Parasitic (nematodes)
• Prion
Bacterial infections - H. somnus
Infectious thrombotic (thromboembolic)
meningoencephalitis
• Et: Haemophilus somnus
• Pneumonia, arthritis, heart abscess….in Bo
• Pathogenesis:
H. somnus invades circulation
Damages endothelium of CNS venules
Subendothelial collagen exposed
Thrombosis, infarction, & vasculitis
CNS hemorrhage, necrosis and inflammation
Bacterial infections - H. somnus
Diagnosis
• Gross and histologic lesions
• Bacterial culture
Bacterial infections - Listeriosis
Listeriosis
• Et: Listeria monocytogenes
• Abortion, septicemia, CNS in Bo, Ov, (Ho)
• Pathogenesis:
•Invasion of oral mucosa
•Cetnripetal intraaxonal migration
•Infection of Trigeminal gang. and brainsteam
•Multifocal suppurative meningoencephalitis
Bacterial infections - Listeriosis
Diagnosis
• Histologic lesions (with Gr + bacteria)
• Bacterial culture
TSE
Transmissible spongiform encephalopathy
• Unique and very unusual dz!!!???
• Scrapie in sheep and goats
• Bovine Spongiform Encephalopathy in cattle
• Chronic Wasting Disease in elk, white-tailed
deer, black-tailed deer and mule deer
• Transmissible Mink Encephalopathy
• Several forms in humans
• Recent reports in other species
TSE
Pathogenesis
• Normal prion protein PrPc is present in
neurons and it has  helix conformation
• Abnormal prion protein PrPres or PrPsc has
 sheet conformation
• PrPres can induce conformational change in
PrPc to become PrPres
• Accumulation of PrPres in neurons causes dz.
• Interspecies transmission depends on in each
PrPc species
TSE
Inoculation
Transmission
Mutation
Inheritance
PrPc
PrPc
PrPc
PrPres
PrPres PrPc
Conformational
change
PrPres PrPres
TSE
What to do if …?
• Submit the animal to a diagnostic lab and
indicate that it is “TSE
suspect”
• If diagnostic lab is far away:
Wear double gloves, mask and eye protection
Decapitate the animal and send the head
Diagnosis
• Histology
• IHC
Viral infections - Rabies
Rabies
• Rabies virus can infect all mammals
• Maintained in nature in reservoir host
(skunks (prairies); foxes (ON), raccoons, bats)
• Pathogenesis:
•Transmitted by bite
•Centripetal intraaxonal migration to CNS
•Infects many neurons incl. Lymbic system
•Centrifugal migration to salivary gl.
•Death is due to progressive paralysis
Viral infections - Rabies
Lesions
• Clin. phases: prodromal, excitatory
(furious or dumb form), & paralytic
• Non suppurative encephalitis
and ganglioneuritis
• Intracytoplasmatic inclusion bodies
Diagnosis
• Fluorescence antibody test
• Mouse or tissue culture inoculation
• Histology & IHC
Viral infections - Rabies
What to do if…?
• Label: “RABIES SUSPECT” and submit
to diagnostic lab
• If you are doing necropsy yourself:
•Should be vaccinated against rabies
•Use double gloves, mask and eye protection
•Never use power tools for brain removal
•Avoid, contact with saliva, brain and CSF
•Submit half brain (frozen) to CFIA
•Other half in formalin
Viral infections - Distemper
Distemper
• Distemper virus, morbillivirus, Paramyxov.
• Dogs, fox, wolf, hyena, ferret, raccoons, etc
• Rarely seen in dogs due to vaccination
• Multisystemic dz (lung, skin, CNS, urinary,
lymphoid tissue
immunosuppression)
Viral infections - Distemper
Pathogenesis
Infection (inhalation)
Replication in tonsils/lungs
Other lymphoid tissues >> immunosuppression
CNS & Epithelia (~ 8-9 days after infection)
Recovery
Death due to
Severe viral infection
+/- 2o bacterial infect.
CNS infection
1o demyelination due to direct viral damage
2o demyelination due to inflammatory reaction
Viral infections - Distemper
Lesions in CNS:
Demyelination (primary and secondary)
Non suppurative encephalitis with
I/N and I/C inclusion bodies
Diagnosis
• Histology
• IHC
Viral infections - WNV
West Nile Virus
• Arthropod-borne flavivirus in birds, Eq, Ho
• Usually no clinical signs in birds
• However, fatal CNS dz. WAS PRESENT in
various birds in the recent US outbreak.
• Lesions: non suppurative encephalitis
• Diagnosis: IHC, PCR,
Serology in live
Viral infections - in utero
In utero viral infections
• Cerebellar hypoplasia
Feline panleukopniavirus
• Cerebellar hypoplasia, hydranencephaly
and/or hypomyelination
Bovine viral diarrhea virus
Hog cholera virus
Blue tongue virus
Border disease virus
Protozoal infections
• Equine protozoal encephalomyelitis
Sarcocysis neurona (defin. host - opasum)
Lesions: necrosis/malacia, inflammation
most frequently in the spinal cord
Diagnosis:
Histological lesions
IHC
Neoplasia
Neoplasia
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Meningioma
Astorcytoma
Oligodendroglioma
Ependymoma
Diagnosis
Histology